The invention relates to an anchor system of a concrete wall formwork with at least one locking device for an anchor bar of the anchor system, wherein the locking device has a threaded nut element for threading the anchor bar through a threaded nut thread of the threaded nut element.
Such anchor systems are used in formwork for steel-reinforced concrete structures. Concrete formwork elements, or formwork elements for short, of concrete wall formworks are made up of a formwork facing and supporting elements, for example, longitudinal girders and tie beams. The two sides of a wall are each formed from one concrete formwork element, that is, a half-formwork, which are held together by anchor bars. The anchor bars are inserted through holes in the formwork facing and fixed at their ends to the elements supporting the formwork facing in such a way that the tensile force exerted on the anchor bars during concrete casting is contained. Normally, the two ends of the anchor bars have threads onto which threaded nuts are threaded as anchor fastenings. This determines the effective length of the anchor bar and therefore the thickness of the concrete wall. At the same time, the pressure exerted during concrete casting by the liquid concrete on the formwork facing is redirected via the threaded nuts onto the anchor bars. The anchor bars are subject to tensile stress during this operation. Between the formwork facings, spacer elements are included in the volume of the concrete wall to be cast that can absorb the compressive forces that occur during concrete casting and mounting of the anchor bars, it being ensured that these compressive forces do not influence the wall thickness in an unwanted way, that is, reduce it.
With the known anchor systems, there are problems with inserting the anchor bar when the concrete wall formwork is erected, if the anchor insertion holes of the formwork elements with their formwork facings facing each other and forming the concrete wall are not sufficiently well-aligned opposite each other.
Because the anchor bar is always inserted from the outside, as seen from the rear of a first formwork element, through the already erected formwork elements, the formwork erector who is positioning the anchor bar cannot see the anchor insertion hole of the second formwork element. The latter anchor insertion hole is found relatively easily but, with poorly aligned anchor insertion holes, the anchor bar extends obliquely with respect to the formwork facing of the formwork elements, making it very difficult to locate the thread of a locking device on the rear of the second formwork element. Moreover, if the anchor bar is oblique in this way, the locking devices cannot lie flat against the formwork elements around their entire circumference, which results in the forces that occur during concrete casting being transmitted to the locking devices concentrated at one point only, which places a heavy load on the locking devices.
A solution to this problem is proposed in DE 10 2007 004 226 A1. Here, too, a concrete wall formwork with a first and a second formwork element, each having a formwork facing, and with an anchor system with an anchor bar and locking devices is disclosed, wherein the formwork elements are disposed opposite each other with the front faces of their formwork facings. Each anchor bar is inserted through a separate anchor penetration hole in the formwork elements. Furthermore, annular sealing elements are provided for sealing the anchor penetration hole in the formwork facings. Each of the locking devices for the anchor bar of the anchor system of the concrete wall formwork has a threaded nut element for threading the anchor bar through a threaded nut thread of the threaded nut element, and a cap plate. The cap plate is fastened to a rear face of one of the formwork elements of the concrete wall formwork. The cap plate has a spherically designed plate region having an opening in which the threaded nut element is disposed having radial clearance, wherein the threaded nut element comprises a groove-like radial circumferential receptacle in which the edges of the opening in the spherical plate region are received. One threaded nut element of each anchor system that is disposed on the side of anchor bar tip, has a tubular guiding device flush with the threaded nut thread of the threaded nut element provided on the end located at the concrete formwork side, which is used to more easily locate the thread opening of the threaded nut head when threading in the anchor bar. Here, however, the problem arises that due to the oblique position of the anchor bar, excessive strain is exerted on the sealing element so that during concrete casting, liquid concrete can escape through the unsealed sections of the anchor penetration holes.
The object of the invention is to provide a locking device for an anchor system and a concrete wall formwork that avoids the disadvantages of prior art, wherein sealing of the anchor penetration holes, through which obliquely positioned anchor bars are inserted, is improved.
This object is solved by the devices of the independent claims. The dependent claims are preferred embodiments of the invention.